If you're just starting back then one workout per day four times a week is probbaly sufficient. After a few months then you can raise the volume, just moniter for overtraining. I've become a big fan of training bodyparts twice per week, start be reducing total sets and adjust based on how well you respond. I've always responded well to volume training so I do more sets than most. Here is my split;
Day 1: Chest and shoulders
Day 2: Back and Bi's
Day 3: Legs and lower back (squat and deadlift are the foundations)
Day 4: off
repeat
I perform twenty plus total working sets for major muscle groups and nine to twelve sets for smaller groups. That's probably too much volume for the average person but it works for me. I never do isolation work for Tri's because I incorporate dips or close grip benches in my chest workout; It just leads to overtraining if I do.